The NASA/IPAC Extragalactic Database (NED) "is built around a master list of extragalactic objects for which cross-identifications of names have been established, accurate positions and redshifts entered to the extent possible, and basic data collected." The main page has links to objects by name and position, data, literature, tools, additional information, and more. Although a bit confusing to use, the database provides an excellent resource for those interested in data of this sort.